Effects of synergetic effect between Co and γ-Fe₂O₃ in confined silica matrix of MCM-41 on the formation of free radicals for the advanced oxidation technology

For the advanced oxidation processes (AOPs), the kind of active radicals is closely linked with the catalytic performance, and thus the formation of free radicals is a key step during the reaction process. In this study, the bi-component catalyst of γ-Fe₂O₃@Co-MCM-41 were successfully prepared by a facile one-pot hydrothermal method, and the synergetic effect between γ-Fe₂O₃ and Co is terrified to be the important factor for the stimulation of different radicals. The results demonstrate that cobalt (II) species are incorporated in the framework, while the magnetic γ-Fe₂O₃ are encapsulated in the silica matrix of MCM-41. Notably, the obvious synergetic effect is built between cobalt and γ-Fe₂O₃ at the adjacent locations inside the silica matrix, and the iron oxides are more reducible. In the peroxymonosulfate(PMS)/Catalyst system, this synergetic effect in γ-Fe₂O₃@2Co-MCM-41 stimulates more reactive radicals of SO₄ ⁻[rad] and [rad]OH, while 2Co/γ-Fe₂O₃@MCM-41 mainly produces SO₄ ⁻[rad]. Both SO₄ ⁻[rad] and [rad]OH radicals are confirmed to be of great advantage to AOPs, thus the γ-Fe₂O₃@2Co-MCM-41 catalyst displays the highest degradation efficiency (0.0778 min⁻¹) in Orange II degradation, which is over three times higher than that of 2Co/γ-Fe₂O₃@MCM-41, and the reasonable reaction mechanism is proposed.